An image forming apparatus using an electronic photograph method such as a copying machine or a printer needs miscellaneous maintenances. Examples of the maintenances are supplement of expendable supplies such as developer, and exchange of a variety of parts that are detachable to the image forming apparatus according to their durability. In the maintenance, the part attached to the image forming apparatus (called an attaching part hereinafter) often contains a storage element which stores registration of a variety of information about the attaching part. In this arrangement, communication is established between the main body of the image forming apparatus and the attaching part via wireless communication or the like, and the image forming apparatus detects the information registered in the storage element. In this way, the image forming apparatus detects the timing for supplement of expendable supplies or the timing for exchanging attaching parts, and also prevents false attachment of the detachable parts (for example, see Documents 1 through 5).
For example, document 1 describes a process cartridge attached to an image forming apparatus, which process cartridge is provided with a storage element in which an IC and a communication antenna are integrally constructed. The process cartridge designates a unit in which at least one of charging means, development means and cleaning means is combined with an electrophotography photo conductor drum inside a cartridge which is detachable to the main body of the image forming apparatus. The storage element contained in the process cartridge is positioned so that it becomes opposite to a communication antenna (called a main body antenna hereinafter) contained in the main body of the image forming apparatus when the above process cartridge is attached to the image forming apparatus. With this configuration, when power is supplied to the storage element, non-contact communication is established between the storage element and the main body antenna.
The above storage element is vulnerable to electromagnetism, mechanic vibration and heat caused by a motor that is a driving source of a conveyor belt used in a production step of a process cartridge, which may cause unwanted change of contents of the information stored in the storage element. In this view, in the document 1, the storage element is mounted to a process cartridge in the final step of fabrication of the process cartridge so as to prevent such defects of the storage element.
The process cartridge described in the document 1, which achieves prevention of the bad influence on the storage element by electromagnetism, vibration and heat in production steps or assembly steps of the process cartridge, however still has a problem of communication noise caused by a variety of electromagnetic waves generated in the environment under which the image forming apparatus is used.
More specifically, general communication between a storage element and a main body antenna uses an electromagnetic wave whose communication frequency falls in a range of AM wavelength (MF (Middle Frequency)). This wave (called AM wave hereinafter) is likely to be influenced by an electromagnetic wave generated by a variety of electric appliances such as TVs, videos, stereos, computers, refrigerators, air conditioners, dryers, and portable phones. As a result, in a room where the image forming apparatus is installed, the above electric appliance becomes the noise source that prevents good reception of AM wave. Such a defect often results in hindrance to communication wave between the storage element and the main body antenna, or interference in electromagnetic induction in the main body antenna, thereby blocking power supply. Therefore, communication error easily occurs between the storage element and the main body antenna.
Further, in the main body of the image forming apparatus, there are miscellaneous noise sources such as a magnetic field generated around motors and a harness, and an electromagnetic wave coming from high-voltage-generating circuits. Particularly, when an electrostatic noise is generated in the image forming apparatus, there is a possibility that the above storage element is destroyed.
Further, when the process cartridge is exchanged according to durability or for supplement of expendable supplies as described above, a spare cartridge for exchange or a used cartridge may be placed near the image forming apparatus. The storage element of this process cartridge, that is not attached to the image forming apparatus but is placed near the image forming apparatus, may also be a cause of hindrance to stable communication between the storage element of the process cartridge in the image forming apparatus and the main body antenna.
As described above, in the environment under which the image forming apparatus is installed, there are various factors generating electromagnetic waves which cause communication noises. Therefore, for a conventional process cartridge, there has been a difficulty in accurately performing information communication between a storage element and a main body antenna.    [Document 1] Japanese Laid-Open Patent Publication 156890/2002 (Tokukai 2002-156890) (published date; May 31, 2002)    [Document 2] Japanese Laid-Open Patent Publication 49206/2002 (Tokukai 2002-49206) (published date; Feb. 15, 2002)    [Document 3] Japanese Laid-Open Patent Publication 117309/2001 (Tokukai 2001-117309) (published date; Apr. 27, 2001)    [Document 4] Japanese Laid-Open Patent Publication 22230/2001 (Tokukai 2001-22230) (published date; Jan. 26, 2001)    [Document 5] Japanese Laid-Open Patent Publication 221938/1998) (Tokukaihei 10-221938) (published date; Aug. 21, 1998)